Oxygen concentrator



FIG. 1 is a top perspective view of an oxygen concentrator, showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a side view thereof;

FIG. 4 is a side view thereof, opposite that shown in FIG. 3;

FIG. 5 is a top thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a rear view thereof. 

The ornamental design for an oxygen concentrator, as shown and described. 